Due to the high cost of energy, there is a continuing need to reduce the cost of making artificial snow, particularly by reduced compressed air consumption. The majority of the ski areas require the use of snowmaking machines throughout the season to ensure complete coverage of the slope and sufficient snow accumulation to ensure excellent skiing conditions on all slopes. A number of snowmaking devices involve electric motor driven fans using little or no compressed air in the process of snowmaking. The initial cost of this equipment is rather expensive, but the expense of operation is generally less than that of the more conventional air/water snow guns utilizing compressed air and water under pressure. Such air/water snow guns are, to the opposite, low in initial cost but much more expensive to operate in terms of the total energy required to operate the same in the production of a given snow volume.
U.S. Pat. 3,760,598 to Jakob et al, issued Sept. 25, 1973, is representative of the motor-driven fan-type of snowmaking machine. A large cylindrical carrier supports interiorly at the inlet end, an electric fan 36 driven by a motor creating a circulation of fan-driven air passing axially through the front end of the cylindrical carrier for the fan and motor. At the outlet end of the cylindrical carrier, a plurality of nozzles open to the exterior of the unit in a direction parallel to the air flow passing through the center of the cylindrical carrier. Compressed air is fed from the manifold to respective nozzles and the nozzles also receive water under pressure from an annular manifold. High pressure air added to the water and discharged from the nozzle in the form of tiny bubbles expands suddenly upon leaving the nozzle to lower the water temperature significantly of the water, leading to a quick formation of ice crystals in the boundary layers between the bubbles of expanded air and the surrounding small droplets of water to generate the nuclei for the promotion of the transformation of water into snow. Further, a nucleating agent may be admixed with the air-permeated water flow, and, in comminuted crystalline form. Alternatively or in addition, a surfactant in powdered or liquid form may be added to the water to reduce its surface tension, thereby facilitating its dispersion into fine droplets and increasing the quantity of snow produced for a given amount of energy required to operate the fan and pump the water and surfactant fed under pressure to the nozzles and compressing the compressed air stream simultaneously fed to the nozzles with the water. U.S. Pat. No. 3,760,598 is exemplary, therefore, of a high-efficiency fan-type snowmaking apparatus.
U.S. Pat. No. 4,353,504 to Girardin et al is an example of the more conventional air/water snow guns with a large diameter cylindrical hollow body which mounts internally a compressed air supply conduit or passageway terminating in an injection nozzle whose discharge orifice is convergent-divergent. A needle valve accommodated inside the compressed air supply conduit or passageway permits precision adjustment of the outlet cross-sectional area of a discharge orifice of the injection nozzle. A pressurized water supply conduit or passageway opens at an angle into the annular space between the hollow body and the central compressed air supply conduit or passageway. The hollow body terminates forwardly beyond the injection nozzle in a frustoconical wall leading to a small diameter mixing chamber aligned with the injection nozzle constituted by the bore of a main nozzle which diverges at its discharge end remote from the injection nozzle.
Various attempts have been made to compromise between the cost of the equipment and the expense in operation. In U.S. Pat. No. 4,383,646 to Smith, water is ejected by impingement into an air stream creating atomization of the water and projection of both water and air. It is known that only a small percentage of the total energy required to freeze the water comes from refrigeration of the decompressing air. The balance of the energy comes from the ambient air in two ways: evaporational cooling and direct heat transfer to the ambient air as a law of mixtures. By increasing relative velocity, the cooling effect is increased. In many air/water snow guns, the velocity of the compressed air leaving the nozzle is supersonic or nearly so with the initial water velocity being generally subsonic. The water then accelerates with the expanding compressed air which establishes one phase of air and water relative velocity within the stream. This defines another velocity relationship to ambient air. However, in a very short time, these relative velocities decrease to only a few feet per second as the adjacent ambient air accelerates and the projected air/water from the nozzle decelerates. Therefore, the evaporational cooling process diminishes to the point given only to the water particles free falling to the surface.
U.S. Pat. No. 4,353,504 to Girardin et al gives increased consideration to the evaporation effects in the design of the nozzle and in terms of the nozzle length. U.S. Pat. No. 3,969,908 to Lawless adds a vortex chamber using compressed air for added air flow around the aspirated water. U.S. Pat. No. 3,774,843 to Wright tends to improve the snowmaking process by confining the compressed air in a chamber for a brief period. U.S. Pat. No. 3,301,485 to Tropeano uses a vortex section for aspirating cold ambient air within that snowmaking device. In U.S. Pat. No. 3,760,598 to Boese, a combination of fan air and compressed air is employed as well as precooled water. In the larger fan devices, a fan supplies large volumes of ambient air for the cooling requirement as well as keeping the water particles aloft for longer periods of time. Such is disclosed by U.S. Pat. No. 4,223,836 to Eager.
It is, therefore, a primary object of the present invention to provide a snowmaking apparatus and method of snowmaking utilizing more of the available BTU's as a result of vaporization of the water while utilizing both extremely small particles for increased freezing rates in conjunction with larger, wetter particles which join for a larger structural snow flake when desirable.